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    <strong>加粗</strong>
    <b>加粗</b>

    <em>倾斜</em>
    <i>倾斜</i>

    <ins>下划线</ins>
    <u>下划线</u></u>

    <del>删除线</del>
    <s>删除线</s>
    <hr>
    <!-- 上标 -->
    X<sup>2</sup>
    <!-- 下标 -->
    H<sub>2</sub>O

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